Abstract: Objective To observe the effect of Xiongdan on blood pressure,vascular structure and dilatation function of mesenteric arteries of spontaneously hypertensive rat（SHR）. Methods Sixteen 12weeks-old male SHR were randomly divided into 2 groups:Xiongdan treated group SHR-X,n=8,800 mg/（kg·d）and untreated group（SHR,n=8）,with age and weight matched Wistar Kyoto（WKY）rats served as control group（WKY,n=8）. All rats were gavaged for 8weeks. Systolic blood pressure was measured by tail-cuff method before and after 4 and 8 weeks of treatment,respectively. The wall-to-lumen area ratios（W/L）and wall thickness-to-lumen radius ratios（WT/LR）of HE stained mesenteric arteries was assessed morphometrically by computer. The vasoactive substance-induced dilation reactivity of mesenteric arteries in vitro were measured at different concentrations by PowerLab biological signal analytical system. Results After 4 and 8 weeks of Xiongdan treatment,systolic blood pressure of SHR-X group was significantly lower than SHR group（176.4±11.4）vs（200.3±13.9）mm Hg at the 4th week;（169.4±12.0）vs（189.9±10.1）mm Hg at the 8th week;both P＜0.01. At the end of the 8th week,W/L and WT/LR of mesenteric arteries of SHR-X group were markedly lower than SHR group（0.53±0.09vs1.82±0.96 and 0.24±0.08 vs 0.53±0.29,respectively,both P＜0.01）,with no statistic difference compared to WKY group（P ＞0.05）. Compared to SHR group,both endothelium dependent relaxation E_max（59.29±15.15）% vs（20.69±6.31）%,pD2（8.24±0.32）vs（5.82±0.23）,respectively,both P＜0.01and endothelium independent relaxationE_max（96.37±1.87）% vs（29.04±4.56）%;pD2（7.79±0.15）vs（5.31±0.14）,respectively;both P ＜0.01of mesenteric arteries were increased in SHR-X group after 8 weeks of treatment.Conclusion The Xiongdan treatment may mildly lower the blood pressure,and ameliorate the vascular structure and dilatation function of mesenteric arteries of SHR.